Illinois Fertilizer & Chemical Association
Supply · Service · Stewardship

Fall Ammonia Season

As soybean harvest commences at a fast rate, fertilization is next on the "to do" list.  
As we continue to work to reduce nitrogen losses in Illinois, fall application of anhydrous ammonia following the IFCA 4R Code of Practice and University of Illinois guidelines is so important!  The research conducted by NREC, and many years of nitrogen rate trials in farm fields throughout the State, shows that having the majority of nitrogen available to the corn plant early in the growing season produces the best response to N.  Fall applied ammonia can be part of this, but to ensure it remains present for the corn in early spring, these recommendations are critical to follow:
1.  Apply when soil temperatures at the 4 inch level fall to 50 degrees and the weather forecast support conditions where soil temperatures will remain cool and trending downward.  Nitrification occurs until soils freeze.  

2.  Do not apply the full nitrogen rate in the fall.  Our industry has done a great job of applying the N rates outlined in the Nitrogen Rate Calculator, but the full rate should not be applied in the fall--save a good part of the rate for spring application, either pre-plant or side-dress.  That way you can minimize environmental risk for your customers and give them the flexibility to adjust and apply the rest of the rate in the spring, based on what the weather conditions are.  

3.  Use a labeled nitrification inhibitor with all fall applied ammonia.  This means N-Serve or Centuro; they are labeled by USEPA with active ingredients that at the prescribed rates on the label, are proven to inhibit bacterial activity that converts ammonium to nitrate.  

IFCA will start posting the daily soil temperatures on our website next week.  We are working with the University of Illinois to outline the timeframe when conditions become appropriate for application, so watch for a Bulletin.  It is not an exact science but we have to continue to be cognizant that research shows that nitrogen applied in the fall can lose nitrate to field tiles, and so this risk must be mitigated by following the best management practices.  

You can always check the soil temps at the Illinois Climate Network but you will need to create an account.  To see the latest UI bulletin on fall fertilizer recommendations, click here.